Various disposable undergarments are commercially available today from various manufacturers for use by adults having problems with incontinence. Examples of such products are men's and women's briefs sold under the trademark Depend® by Kimberly-Clark Corporation. The Depend® products utilize a chassis mounting an absorbent core in the crotch region of the chassis. The chassis itself comprises a colored nonwoven with approximately fifty seven transversely extending strands of white spandex elastic threads laminated between layers of a nonwoven spunbond fabric to impart elasticity to hold the undergarment close to the body of the wearer. The spacing between the elastic fibers is relatively large, e.g., 6-7 mm, so that the chassis exhibits a somewhat puckered appearance.
Other manufacturers provide similar types of undergarments making use of chassis for holding an absorbent core, wherein the chassis includes a plurality of transversely extending elastic threads or filaments to render the undergarment close-fitting in the interest of concealability and wearer comfort. For example, Proctor & Gamble offers incontinence underwear under the trademark Always®. That product also makes use of a chassis comprising approximately fifty seven transversely extending and relatively widely spaced strands of white spandex elastic threads sandwiched between two layers of a nonwoven spunbond fabric. The chassis mounts an absorbent core and includes six additional colored elastic threads in the rear of the chassis to serve as an indicator of the back side of the product. Like the Depend® products the Always® products also exhibit a somewhat puckered appearance.
Livedo, USA offers an incontinent brief under the trademark LivDry™. That product makes use of a chassis having approximately forty widely spaced transversely extending white spandex elastic strands in panels laminated between two layers of white spunbond fabric, plus an additional eight colored elastic spandex strands in the rear of the product to serve as an indicator of the back side of the product. Like the Depend® products and the Always® products, the LivDry™ products also exhibit a somewhat puckered appearance.
Kimberly-Clark manufactures two other adult incontinence products under the names: Depend Silhouette and Depend Real Fit. Both products employ an elastic meltblown film fabric-like material that is difficult to process, has higher cost and has limited stretch.
Moreover, many current adult disposable absorbent products, utilize what is known as a fiberized bleached wood fluff pulp and a SAP (Super Absorbent Polymer) mixture for the absorbent core. At low ratios of 30% or less SAP to pulp ratio, the core mixture may or may not be wrapped in an absorbent tissue to prevent the SAP from falling apart or out of the core. At higher levels of SAP at 50% or more, the core must be wrapped to prevent the loose SAP from being shaken out. Also a core adhesive may be added to prevent the heavier SAP particles from being separated from the fluff pulp fibers. The pulp fiber in these products is required to rapidly manage the body fluid exudates until the SAP can desorb the fluff fibers to prepare the fluff fibers for the next exudates. For an adult the amount of exudate is can easily exceed 300 ml. or more delivered over a time period of more than 70 seconds at a rate similar or less than what infants void.
A significant problem with the current absorbent products that contain wood fluff pulp or even wrapped with a tissue or air-laid is in all cases their construction results in a core which feels wet against the body after it has received the voided fluid(s). To address this wet feel, almost all current absorbent product designs employ a distancing layer of synthetic fibers on top of the “wet core” as an attempt to create a “feel drier” layer. This synthetic distancing layer is often called a “fluid transfer layer”, “fluid acquisition layer”, or “acquisition distribution layer (ADL)” and is typically much smaller than the core that it covers, leaving the edges of the core exposed. Moreover, despite their design goal, such fluid acquisition layers only work to a limited degree. In this regard as the exudate leaves the body at 98 degrees Fahrenheit it quickly drops to about 90 degrees Fahrenheit as it enters the core of the absorbent product. This creates a cooling effect when touched by the skin, which may increase during the time worn. If left on for an extended period of time, the wet product will achieve a thermal equilibrium and equilibrate somewhere between room temperature and about 90 degrees Fahrenheit, depending upon ambient temperature and clothes worn. This difference can be further exacerbated depending upon the thermal conductivity of the materials chosen to absorb the exudate. But in all cases current wood pulp fluff absorbent products will feel wet and/or cold to the skin the longer the product is worn.
The current state of the art product design for the synthetic absorbent cores is based upon a synthetic continuous fiber matrix inter-layered with SAP. For example a polypropylene tow fiber similar to tow used in cigarette filter making was chosen. This material is purchased in a continuous form and is pulled out of the box and proceeds into an air trumpet or similar device or the like, to expand the fiber tow matrix. Then SAP particles are intermixed, adhesive is sprayed into the fiber SAP matrix and the entire matrix is wrapped to result in what is the state of the art of current so-called “pulp-less” core technology. This type of core has the major limitations of a slow absorbency rate. That rate is highly dependent upon the SAP chosen and on the adhesive type and amount required to attach the SAP to the tow fiber matrix. For example, if enough adhesive is provided to ensure that the SAP remains in its desired location within the core, that adhesive may limit the SAP's absorbent swelling due to coating part of the SAP particles. If less adhesive is utilized, while it may permit greater swelling and absorption of the exudate by the SAP, it may allow the SAP particles to fall from their positions in the core to the bottom of the crotch area, rendering it heavier and wetter in the crotch area when voided into and less absorbents at the ends.
Another example of current pulp-less core technology is gluing the SAP to the back sheet or inside the top or body facing sheet. This bonding process may limit the SAP from being fully expanded and utilized in absorbing the exudate. When bonded in such a matter, the SAP may also be applied in continuous rows to provide space for the fluid to travel unhindered. Or the SAP may be intermixed with ground wood pulp fibers of similar size to enhanced fluid movement in this inefficient design.
Current SAP limitations require having to choose between a higher absorbent capacity, with the disadvantage of having slower speed, or a faster SAP with less absorbing capacity. If the current SAPs are mixed, the fast acting SAP will very rapidly swell and may “gel-block” the slower acting, but higher absorption capacity SAP. If gel-blocking occurs, it will limit, or even prevent, the higher capacity SAP from desorbing the faster but lower capacity SAP.
In the past a cellulose acetate fiber core with a single SAP has been developed and commercially available, as has a non-SAP version. Current polypropylene filament tow technology has also been used for the absorbent cores. In this regard, such polypropylene tow cores used in the market today make use of round or oval homo-polymer polypropylene fibers, which provide minimal resistance to fluid flow through the SAP/tow fiber matrix, thereby only providing minimal dwell time for the fluid to be absorbed by the SAP.
While the aforementioned prior art products are generally suitable for their intended purposes, they nevertheless leave something to be desired from the standpoint their ability to absorb voided liquids quickly, easily and effectively without leakage, in an undergarment which is comfortable, thin, aesthetically pleasing and highly concealable under outer clothing. Thus, a need exists for disposable undergarments that address those needs.
The subject invention addresses those needs by providing a undergarment whose chassis includes a much larger number of transversely extending elastic strands, which are spaced closer to one another to provide a significantly improved fit to the wearers body, while at the same time providing a flatter appearance than the puckered look of the prior art incontinent undergarments. Moreover, the chassis mounts an absorbent core which is composed of two sections of SAP for quickly and securely absorbing voided liquid without leakage. To that end, one section of the core, which is located facing the wearer's body, includes a plurality of pockets partially filled with a free, slow acting, but highly absorbent SAP. The other section of the core is located facing away from the wearer's body and includes a plurality of pockets partially filled with a free, fast acting, but lower absorbency SAP. With this construction, liquid voided into the core is initially quickly absorbed by the fast acting SAP section, whereupon the section with the slow acting, but high absorbency SAP desorbs the section with the fast acting SAP to securely contain the voided liquid therein and prevent any leakage out of the core.